Condition-responsive electrical control device



Dec. 1, 1959 R. B. COLT ETA!- 2,915,725

CONDITION-RESPONSIVE ELECTRICAL CONTROL DEVICE Filed April 18, 1957 2 Sheets-Sheet l INVENTORS RUIGER B. COLT 4,, Trggms K.KJELLMAN Maw ATTORNEY CONDITION-RESPONSIVE ELECTRICAL CONTROL DEVICE Filed April 18, 1957 Dec. 1, 1959 B, COLT EI'AL 2 Sheets-Sheet 2 FIG. 5.

INVENTORS RUTGER B. COLT THOMAS K. KJELLMAN ATTORNEY Secs P Colt and Thomas K. Kiellman, Baltimore, Md., assignors to Bendix Aviation Corporation, Baltimore, Md., a corporation of Delaware Application April 18, 1951, Serial No.

2 Claims; (Cl. 338-41) This invention relates to an electrical control device for varying the resistance of an electric circuit as a function of changes in some condition or parameter, such as altitude, manifold pressure and the like.

In many installations involving electrical control circuits, cost and space requirements render it necessary to utilize control units which are relatively small and extremely simple in construction while at the same time the unit must perform its necessary function accurately over long periods of use; and an object of the present invention is to provide a condition-responsive control or regulating device which will meet these requirements.

Another object is to provide a highly sensitive, compact pressure-responsive electrical control device in the nature of a combined rheostat or potentiometer and pressure-responsive capsule in which the capsule acts directly on al'contact arm, which in turn rocks or rolls on a resistance-varying element with a minimum of applied force and a controllable amount of. friction.

Another object is to provide an electrical control device of the pressure-responsive type in which the change in resistance for a given-change in pressure is dependably uniform over the entire range of the device and may be linear or have a predetermined degree of non-linearity, as desired. i

A further object is to provide a combined pressure-responsive capsule and electrical resistor assembly of the rocker type which is simple yet accurate and capable of easy adjustment.

The foregoing and otherobjects and'adva'ntages will become apparent in view of the following description taken inzconjunction with the drawings, wherein:

Figure 1 is a top plan view of a pressure-responsive control device in accordance with the invention;

Figure 2 is a view in section taken on the line 2-2, Fig: l; but with the top of the case and the pressure-responsive capsule broken away to expose the resistor-as- 'sembly therebelow;

Figure 3 is a view in edge or side elevation of the device of Figures 1 and 2, with parts broken away; and

Figure 4 is a detailed perspective view of the resistor assembly and the housing or case in which it is mounted.

Referring to the drawings in detail, a deeply-dished outer casing or housing is generally indicated at 10, which in practice is made of relatively thin-gauge sheet metal, preferably aluminum, to promote lightness in weight. The top wall of the housing is contoured to receive a pressure-responsive capsule 11, which is made up of a pair of opposed diaphragms joined at their meeting edges, providing a peripheral flange 11'. The top wall of the diaphragm, has secured thereto a which is threaded through the top wall of the casing and has applied thereover a lock nut 13, by means of which the position of the diaphragm may be adjusted vertically within the casing. The bottom of the capsule, or the lower diaphragm, has projecting downwardly therefrom a pointed or tapered contact member 14, which bears against a contact area 14, formed on a 2,915,725 Patented Dec. 1, 1959 contact arm 15 of conductive material, which has an arouate contour longitudinally thereof and is also arcuate oi' channel-shaped in transverse cross-section, for a purpose to be explained in the description of operation. It will be noted that the contact area 14 lies a plane normal to the vertical line of thrust of the pointed contact member 14. At its one end the arm 15 is provided with a pair of parallel pivoting or hinge lugs 15', through which a pivot pin 16 projects and by means 0" which the said lever is pivotally mounted on the upwardly-projecting end portion 17 of a leafspring 17, the opposite extremity of said spring slanting upwardly and term'inating in a curved contact tip or end 18, which bears against a small pivotally-mounted hollow resistor rod 19 carrying a resistor 19, which in the example shown is in the form of closely-spaced resistance wire wound on the free extremity of said rod. Theparts '15, 17 and 19 comprise an assembly which is mounted within a cavity 20, formed in an inner case 21, the latter in practice being made of thermoset'ting" plastic or similar material. The cavity 20 terminates at one end (the left-hand end as viewed in Fig. 2) in a recess 22, in which the one end of the resistance rod 19 is situated and pivotally anchored by means of a pin 23', which is projected through the opposed walls of the case at this point. The spring 17 is anchored to the base of the case "21 as at 24.

An adjusting screw' 25 is threaded through the assemsly-supporting case 21 and abuts the u "wardly projecting arm 17 of the spring 17 to which the lever 15 is pivotally connected.

The case 21, which supports the resistor assembly, telescopes within the inverted cup-shaped outer casing 10 and is held in place therein by means of screws 26.

A pair of terminals 28 and 29 are fixed to the case 21, the terminal 28 connecting with theone end of the resistance wire 19' by means of a wire 30, while the terminal 29 connects with the one end of the arm 15-by means of a wire 31. Insulated lead wires 32 and 3 3 conneet with the terminals 28 and 29 and are' adapted to be connected int'o'the electrical circuit to be controlled. A third wire 34 connects with the end of the resistor 19 opposite that to which the wire su'iscomrected and is bi'ought olit through the hollow rod 19 and attached to a terminal 35. In the event the control deviceis'to be used'as a rheostat, terminals '28 and29 only are connected'in circuit, whereas if it isto be used as a potentiometer,'terminal 35' is also connected into the circuit'to becontrolled in a manner well known to those having a laymans knowledge of the electricala'rt.

Operatibn In practice, the device shown herein is used to vary the resistance of an electrical circuit as a function of changes in altitude, the said circuit being part of a direct injection system for controlling the flow of fuel to the internal combustion engine of a motor vehicle. The range of control extends from ground level to a height or altitude of say 15,000 feet. In the position of the parts as shown in Fig. 2 of the drawings, the contact arm 15 is in its high-pressure position with respect to the resistor 19', this being the ground level or near ground level position. As altitude is gained, the capsule expands and rocks the arm 15 in a counter-clockwise direction on the wire-wound resistor 19 carried by the rod 19, the transversely-arcuate or channel-shaped contour of the arm 15 and the rounded contour of the resistor causing the arm and resistor to mate and track" one another and effect a uniform contact action for each increment of movement of the capsule 11. The free fioatingmounting of these elements facilitates this tracking action. That portion of the leaf spring which urges the rod 19 and its resistor 19' upwardly against the arm 15 need have only sufficient of assembly shown.

In the form of the device shown, it can be assumed that there is just enough friction developed between the contact surfaces of the arm 15 and the resistor 19' to ensure automatic cleaning, or prevent the build-up of an insulating film on these surfaces. Ordinarily, the amount of friction developed for this purpose produces no appreciable wear.

spring 17, which 1n turn repositions the travel of the capsule and the preset relationship of the contact arm 15 and resistor 19' remains undisturbed.

e entire assembly is light in weight, compact and easily fabricated by ordinary production personnel.

at is claimed is: 1. Means for varying the resistance in an electrical circuit in response to changes in a condition comprising:

sistor and arm are caused to accurately track one another during the traversing action, and means connecting said resistor and arm in said circuit.

2. Means for varying the resistance in an electrical circuit in response to changes in a condition comprising:

ber.

References Cited in the file of this patent UNITED STATES PATENTS 2,286,717 Clason June 16, 1942 2,392,937 McDaniel Jan. 15, 1946 2,466,846 Giesler Apr. 12, 1949 FOREIGN PATENTS 1,049,620 France Dec. 30, 1953 

